Semi-trailer trucks are well known throughout the world in which an independent truck trailer can interchangeably be connected to practically any desired truck cab for transporting the trailer and it contents to any desired location. While the truck cab and truck trailer can take any one of a large variety of different forms and sizes, depending on the intended use and intended load to be transported, the interconnection between the cab and trailer has developed into a uniform standard design so that the cabs and trailer can readily be interchanged according to need. Pursuant to this standard form, the truck cab is normally provided with a chassis structure such that a portion of the truck frame extends rearwardly of the cab with one or more drive axles, upon which wheel and tires are mounted, supporting the truck cab on the road surface under the rearwardly extending portion of frame structure. A tiltable, steel disk, commonly referred to as the "fifth wheel", is horizontally disposed on the upper side of the rearwardly extending frame portion, with the fifth wheel having a diverging "V" slot extending rearwardly from an aperture at the axial center.
The truck trailer, on the other hand, is normally provided with one or more rear axles, to which wheels and tires are mounted, for supporting the rear-end of the trailer on the road surface. When interconnected, the front end of the tuck trailer is supported on the fifth wheel mounted on the rearwardly extending portion of the cab frame such that the rear cab axle or axles support the load in the front-end portion of the trailer. A king pin extending downwardly from the under surface of the trailer near the front thereof is adapted to be engaged within the aperture on the fifth wheel, so that the trailer can be pivotally connected to the cab and pulled thereby in an articulated manner. For friction reducing purposes, the upper surface of the fifth wheel is normally greased heavily, as in its articulating action, the forward portion of trailer undersurface must be free to pivotally rotate against the upper surface of the fifth wheel. To support the truck trailer in the absence of a cab, the front end of the trailer is normally provided with a crank-down support means disposed rearwardly of the king pin, which can be manually operated to lower the support means to a vertical orientation, to thereby support the forward end of the trailer.
To connect the truck cab to the truck trailer, the front end of the trailer must be supported on the crank-down support means, or other such support, such that the king pin extends downwardly from the front of the trailer floor spaced above the road surface by a distance sufficient to permit the fifth wheel on the cab to be backed under the king pin. The diverging "V" slot in the fifth wheel is designed so that upon driving the truck cab in reverse, the driver can guide the "V" slot around the king pin extending downwardly from the front end of the trailer, and guide it to the aperture at the axial center, where a spring loaded locking mechanism secured to the lower side of the fifth wheel will lock the king pin in place within the aperture, thereby also holding the forward undersurface of the trailer against the upper surface of the fifth wheel. When so locked together, the truck cab and truck trailer can readily function as an articulated semi-trailer truck. The locking mechanism on the undersurface of the fifth wheel is well known in the art and need not be described here.
To disconnect the truck trailer from the track cab, an elongated release rod is horizontally disposed at the under surface of the fifth wheel which emerges through an opening in the side wall of the fifth wheel. One end of the release rod is connected to the above-mentioned spring-loaded locking mechanism, with its other end extending through the side wall opening on the fifth wheel, and having an eyelet at its outer end, to which a release tool can be attached. The release rod is normally transverse to the center-line of the truck cab, so that the side wall opening and eyelet are normally located on the left side of the cab between the upper surface of the cab's left-rear tire or tires and the under surface of the trailer resting on the fifth wheel.
To physically and manually release and disengage the truck trailer from the fifth wheel, a release tool, which comprises an elongated steel rod having a hook at one end and a hand-grip at the other, is hooked into the eyelet at the outer end of the release rod, and the tool manually pulled so that the release rod will pull on the locking mechanism to disengage the trailer king pin. When so disengaged, the truck cab can be driven in a forward direction from under the trailer. Obviously, the crank-down support means under the trailer must first be positioned so that the front end of the trailer will be supported on the road surface when the cab is driven away therefrom, and in ready position to permit the same or another truck cab to later be attached thereto.
While such a disengaging effort is not particularly difficult, it is not as simple and easy as could be hoped for. For example, to engage the release tool into the release rod eyelet, the truck operator must normally stoop over so that he can see the eyelet which is normally positioned under the bottom surface of the trailer and over the cab's rear tire or tires, and then reach therebetween to engage the hook into the eyelet. This can be unpleasant and complicated in the darkness of night, or during fowl weather situations where snow and/or ice may be packed in and around the fifth wheel or between the cab rear tires and the trailer. In addition, it is not uncommon for the release tool hook to slip from the release rod eyelet when not properly engaged, causing the driver to injure his back, hit his head on the trailer, or hit his knuckles or arm against the trailer or tires. In addition further, it is not uncommon for the release tool to be lost, stolen or misplaced, making it impossible to release the trailer until a release tool is located. Because of the grease that must be utilized between trailer and fifth wheel interfaces, the area in and around the fifth wheel is often rather greasy and mixed with road dirt, so that in addition to mud that may be on the cab tire surfaces, the above described release effort can also be a rather messy task.
In addition to the above problems, it should be noted that many of the prior art release rods are provided with a stop bar welded to the underside which functions as a lock to prevent unintentional pulling of the release rod. Specifically, the stop bar is of shorter length than the release rod so that the outer blunt end thereof will abut against the edge of the hole through which the release rod extends to thereby prevent the release rod from being pullable outward unless it is also lifted upwardly to an extent sufficient to permit the stop bar to also fit through the hole. That is to say, the hole is normally elongated in the vertical direction so that when lifted, both the release rod and stop bar will easily fit therethrough. In a like manner, the opposite blunt end of the stop bar will abut against the outer hole edge to thereby prevent the spring loaded locking mechanism from pulling the release rod inward, which in essence locks the release mechanism in the king pin "release" position. It should be apparent, that it is rather difficult to effect the required lifting action together with the pulling action when using the conventional release tool merely hooked to the eyelet of the release rod, particularly in view of the rather restricted space that may exist between the truck cab rear tires and the bottom of the trailer.
Our co-pending patent application, Ser. No. 08/584,421, filed Jan. 22, 1996, teaches a new and improved apparatus intended to be permanently mounted to the fifth wheel of a truck cab for quickly, easily and more safely disconnecting a trailer king pin from the fifth wheel of the truck cab. Accordingly, the apparatus of that invention eliminates the need for a separate tool; i.e., a release tool, thereby avoiding the complications and lost time that can result from a lost, stolen or misplaced release tool, and further eliminates the sometimes complicated or unpleasant task of hooking the release tool to the eyelet on the release rod, as noted above. In addition, that apparatus, in using a lever arm to pull the release rod outwardly, can very easily be utilized to effect the necessary lifting action to disengage the stop bar as described above, making the entire release activity an effortless task. More importantly, that inventive apparatus further eliminates the possibility of injury that can result to the operator when the release tool hook slips from the release rod eyelet during the disengaging effort.
In essence, the apparatus of that invention comprises an elongated, rigid lever arm, a first end of which is pivotally attachable to a side of the fifth wheel at a location spaced from the opening through which the release rod emerges, and a second end adapted to be spaced away from the fifth wheel extending generally horizontally from the first end, and including means thereon for attaching the lever arm to the elongated release rod, such that a manual motion applied to the lever arm at the second end, can cause the lever arm to be pivoted generally horizontally at the first end, thereby causing a levered pulling action on the release rod so that the release rod is pulled outwardly sufficient to disengage the king pin from the fifth wheel.
While the inventive apparatus described above has been shown to provide very significant advantages over the prior art, some shortcomings have been noted. Specifically, it has been found that the desired length of the lever arm varies depending upon the size of the truck cab and the number of drive axles at the rear of thereof. With a single drive axle, lever arm lengths of about 4 to 5 feet are quite adequate. On the other hand, such lever arms on truck cabs having tandem drive axles or tri-axles tend to be unnecessarily short so that the user must still reach under the trailer, not only to grasp the lever arm, but even when fully pulled outward it may still not sufficiently clear the trailer and cab rear axles to avoid all difficulties.
In addition to the above, it has also been noted that the moment of inertia resulting from the weight of the lever arm extending from the single bolt holding the apparatus against the side of the fifth wheel, tends to cause the apparatus to sag and twist at the bolt, thereby loosening the bolt and intensifying the sagging movement so that the entire apparatus can quickly become excessively loosened.
As a third problem, it had been observed that the elongated release rod as attached to the original lever arm was attached at a fixed single point so that the pivotal movement of the lever arm caused an arcuate displacement of that fixed single point. As a result, the arcuate displacement of the lever arm pulling the release rod out from the fifth wheel has tended to bend the release rod somewhat which may interfere with its being drawn back inward by the spring loaded lock mechanism.